Method for ocular perfusion

ABSTRACT

Ocular perfusion during intraocular surgery of the anterior or posterior ocular cavity is optimized through the method of using a gas pump having a discernible and controllable output pressure to pressurize a reservoir of liquid infusate, which is supplied under pressure to a surgical infusion instrument for perfusion of the selected ocular chamber (Gas Forced Liquid Infusion, GFLI). The infusate selection and the infusate pressure can be controlled with a high degree of accuracy and both can be rapidly varied by audible command. Preferentially a human sensible indication of pressure is constantly available at the gas pump.

This is a continuation-in-part application of Ser. No. 099,533 filedSept. 22, 1987 now allowed U.S. Pat. No. 4,813,927 entitled "PARALLELINFUSION APPARATUS AND METHOD".

FIELD OF THE INVENTION

The present invention relates generally to apparatus and methods used insurgery conducted on the eye. More particularly, the present inventionrelates to apparatus used in continuous infusion processes associatedwith such surgery. In even greater particularity, the present inventionrelates to apparatus for accurately and rapidly controlling the infusionpressure to the eye and rapidly converting between liquid and gasinfusion during such surgery.

BACKGROUND OF THE INVENTION

Intraoperative control of intraocular infusion pressure is an importantparameter in eye surgery. Liquid pressure regulation has beenaccomplished in most part using gravity-fed systems involving therelative height of the infusion bottle above the eye. A discussion ofthe development of gas infusion may be found in "Vitreous Microsurgery"by Steven Charles, M.D. in Williams & Wilkins, 1981, volume 4. As notedtherein, there are known power injectors or pumps which are capable ofmaintaining an accurate intraocular pressure during air infusion, ascompared to manual syringe injection. Such devices have also beendeveloped wherein a microcompressor is used to product an inflow of gasdependent upon intraocular pressure.

As these advances are made in gas infusion apparatus, a need exists forcontrolled intraocular infusion method and apparatus which wouldfacilitate the interchangeability of gas infusion and liquid infusionduring surgery on the posterior segment of the eye (vitrectomy).Additionally, during surgery on the anterior chamber of the eye(cataract extraction) the need exists for more accurate, surgeoncontrolled and monitored liquid infusion.

During cataract surgery, the most common operation performed in theUnited States, the surgeon views only the anterior chamber of the eye asshown in FIG. 5, having no method of simultaneously monitoring theposterior segment.

Since the anterior chamber is quite small, containing only 0.25 cc ofliquid volume, small and momentary aspiration flow rates exceedinginfusion rates will result in anterior chamber collapse, as shown inFIG. 5. The consequence of anterior chamber collapse is damage to thenonreproducible monolayer of cells (endothelium) which lines the innersurface of the cornea, keeping it clear of fluid. This endothelialdamage can then result in clouding of the cornea, with the need forsubsequent cornea transplantation.

It is common for contaract surgeons to perform incomplete temporaryclosure of the surgical incision prior to irrigation/aspiration cataractcortex removal. A true "closed-eye" system is never achieved, andanterior chamber collapse in this condition is a sign of wound leakageof infusion liquids rather than of inadequate infusion pressure. Ifanterior chamber collapse is encountered, the wound should be checkedfor tightness.

The cataract surgeon's most common defense against perceived anteriorchamber collapse is increasing of infusion pressure by raising agravity-feed infusion bottle an estimated height above the eye as shownin FIG. 4. Note that gas is not commonly infused into the anteriorchamber in such surgery. In practice, bottle height is not measured, sothat actual pressure delivered to the eye is unknown, and is presumed tobe sufficient when anterior chamber collapse no longer occurs.

Unfortunately, corneal endothelial damage may also occur as a result ofhigh infusate volume or jetstream mechanical damage from the use of highflow rates under high pressure. These effects, moreover, are not readilyapparent to the surgeon due to his inability to perceive the flow rateor pressure. Retinal artery occlusion may also occur, invisible to thesurgeon and resulting in blindness. Finally iris prolapse through thewound may occur as a result of excessive infusion pressure.

Ideally, cataract irrigation/aspiration surgery should be performed withnormal ocular pressure (25 mm Hg). Failing this, infusion pressureshould be raised as little as possible to maintain anterior chamberpressure to avoid collapse during active irrigation/aspiration. Becauseunnecessarily high infusion pressure and flow rates can injure retinaland corneal tissues with little warning to the surgeon, increasinginfusion to the eye should be the last solution attempted to remedyanterior chamber collapse. As previously stated, the surgeon shouldfirst check adequate wound closure. Further, even with an adequatelyclosed eye, anterior chamber collapse may occur as a result ofundisciplined, continuous, high rate aspirations. High vacuum aspirationis necessary to achieve cataract removal, but successful removal ofblocks of cataract cortex material (with subsequent opening of theaspiration port) should be anticipated so as to intermittently reducethe aspiration vacuum, avoiding anterior chamber collapse. All toocommonly surgeons move about within the eye with an open aspirationport, with suction continuously engaged.

The above discussion demonstrates the importance of a new method ofrapid, accurate, surgeon controlled ocular infusion (Gas Forced LiquidInfusion, GFLI).

SUMMARY OF THE INVENTION

The primary object of the invention is to provide the surgeon with amethod and apparatus to rapidly and precisely control and monitor hisinfusion pressure.

It is also an object of the present invention to enable the surgeon toquickly switch between liquid infusion and gas infusion.

Yet another object of the invention is to enable the usage of momentarymaximum safe infusion pressure for such purposes as controlling bleedingduring surgery.

These and other objects and advantages are accomplished in our inventionthrough a novel arrangement of conduits and valves which allow theconstant maintenance of the desired intraocular pressure and theflexibility of using either gas or liquid infusion. The inventionutilizes an infusion bottle as a reservoir for the infusion liquid. Acontinuous infusion gas pump, such as a Grieshaber or Trek Air Pump, isutilized to pressurize the liquid infusion bottle to the desiredinfusion pressure (Gas Forced Liquid Infusion, GFLI). The output of thepump is also used directly to provide pressurized gas via a conduit forgas infusion to the eye. A conduit from the infusion bottle providespressurized liquid for infusion. The gas conduit and liquid conduit arepreferentially formed as a dual-tube conduit and are connected to astopcock which allows the physician to select either gas infusion orliquid infusion.

In an alternate embodiment, adapted for anterior chamber surgery, thegas infusion line is eliminated since gas infusion is not commonly usedin this type surgery; the flexible conduit connections between theliquid infusate bottle and the eye, and between the gas pressure deviceand the liquid infusate bottle are maintained. In both embodiments, theoutput of the gas pump is connected directly to the pressurized gaspocket above the infusion liquid via a conduit extending within theliquid infusion bottle

BRIEF DESCRIPTION OF THE DRAWINGS

Apparatus embodying features of our invention are depicted in theappended drawings which form a portion of this invention and wherein:

FIG. 1 is a perspective view showing the apparatus as used duringsurgery;

FIG. 2 is a broken lay-out view showing the invention not in use;

FIG. 3 is a broken lay-out view showing the cataract surgery embodiment;

FIG. 4 shows the prior art and ocular structures; and

FIG. 5 shows an instance of ocular collapse.

DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 4 illustrates the common control methodology and apparatus forliquid infusion of the eye as heretofore used in cataract and invitreous surgery. FIG. 5 is illustrative of common ocular collapse whenusing the method and apparatus shown in FIG. 4.

Referring to the figures for a better understanding of the invention, itmay be seen that the invention is for use with a patient who is lyingbeneath surgical drapes 11 on an operating table 12. A continuousinfusion air/gas pump 13 is located on an equipment stand 14 as isconventional practice. The output of the air/gas pump 13 is displayed asby LED's at a panel 16 so that the pressure generated thereby may bemonitored by the surgery team and precisely controlled.

The output of the air/gas pump 13 is used to pressurize a liquidinfusion bottle 23 to provide Gas Forced Liquid Infusion (GFLI) of theeye. Use of Gas Forced Liquid Infusion (with digital numeric readout ofinfusion pressure in view of the surgeon) allows the surgeon for thefirst time to accurately and continuously monitor this most importantparameter. In this method, the infusion bottle is hung at eye height, sothat gravity feed, the preferred technique of the prior art, contributesno pressure to perfusion/infusion. Rather, total control of perfusionpressure is instead achieved by instilling in the infusate bottle, gasunder pressure, provided by the gas pump. The infusion pressure canthereby be meticulously and rapidly selected by the surgeon.

An antibacterial filter connector 17 attaches a flexible conduit 18 tothe pump 13 in any conventional manner as is well known in the art. Theconduit 18 extends from the equipment stand 14 to near an IV support 19and terminates in a T-connector 21 or other suitable device fordirecting the airflow from the pump 13 along two paths. A fluidpressurization conduit 22 is connected between the T-connector 21 and acombined infusion bottle with drip chamber 23 supported by the IVsupport 19 and serves to pressurize the fluid therein in accordance withthe output pressure of the pump 13. This fluid pressurization conduitextends within the infusion bottle so as to connect the gas volume aboveliquid with the gas pump for venting purposes. A fluid delivery conduit24 is connected as the output of infusion bottle 23 and terminates asone input to infusate stopcock selection valve 26. An air deliveryconduit 27 is connected between the remaining branch of the T-connector21 and the valve 26. Note that valve 26 may be a three-way input valvewhich would allow selection of either liquid, air, or finally an air/gasmixture (e.g. sulfur hexafluoride SF₆ 20%, perfluoropropane C₃ F₈ 15%)delivered by a second gas pump. The valve 26 has a single output to aninfusion conduit 28 which is connected to and supplies an eye infusioncannula 29.

As shown in FIG. 1, the infusion bottle 23 is placed at the patient'seye level so as to contribute no gravity infusion pressure as had beencustomary in the prior art. Air/gas is pumped into the bottle 23 viaconduits 18 and 22 to provide the desired infusion pressure. Although anormal starting pressure may be selected, it should be clear that theinfusion pressure can be rapidly changed by adjusting the outputpressure of the air pump 13. The air pump selected should have a digitaldisplay 16 of the pressure which should be visible to all operating roompersonnel. It has been determined that the displayed, conduit, andintraocular static pressures agree to within two to four mm of Hg usingthe present apparatus.

Valve 26 allows the surgical team to quickly switch from liquid infusionto gas infusion. Conduits 24 and 27 may be formed from the two halves ofa twin plastic tube, for example Dicoc Twin Bore Silicone IV tubing,such that the valve 26 may be located immediately proximal to the shortcannula 29, thereby minimizing the time and volume required to clearinfusion liquid from the system cannula 29 when gas is desired.

From the foregoing, it may be seen that we have provided an effectiveapparatus and method (Gas Forced Liquid Infusion, GFLI) which greatlyimproves the surgeon's efficiency in vitrectomy operations in whichliquid to gas infusion changes are desired and also provides a readilycontrollable means for varying the infusion pressure during all liquidinfusion eye surgery including cataract removal. As is well known, it ispossible to stop or reduce bleeding by raising the intraocular pressureto maximum known safe levels, usually 35 to 45 mm of Hg. Using thepresent invention with a digital display 16 allows the surgical team toquickly determine the infusion pressure levels and rapidly change thelevel as required, to maximum safe level with great accuracy.

It is the aspect of the invention that allows the surgical team tocontinuously monitor and precisely control the infusion pressure whichis of critical importance to the cataract surgeon. The tubing systemshown in FIG. 3 uses an antibacterial filter connector 31 to attach aflexible tubing 32 to the air pump 13. The flexible tubing 32 isconnected directly to the infusion bottle 23 which is supplied withinfusion liquid as shown in FIG. 2. A single flexible conduit 33 isprovided to carry pressurized infusion liquid from the bottle to a valve34 which controls the flow of liquid to the infusion/aspiration device36 used in cataract surgery. With the digital readout 16 available thesurgeon is able to constantly monitor the pressure being utilized in theeye and therefore is at all times aware of and alert to the potentialdeleterious consequences of overpressurization and jetstreaming. Thus,due to his ability to monitor and accurately select the intraocularpressure, the surgeon will naturally turn more attention to adequatewound closure and disciplined aspiration rather than using a potentiallydestructive infusion pressure level to prevent ocular collapse.

The use of the gas pumps 13 to pressurize the infusion bottle 23 ineither of the embodiments above also leads to a significant furtherrefinement in the art. Voice recognition technology can be used toregulate the output pressure of the gas pump 13. Thus, an inputmicrophone 37 is connected to a voice recognition circuit, many of whichare commercially available, which in turn outputs a control signal tothe pump 13. Preferentially the pump will be provided with a speaker 38which will enunciate the pressure, subsequent to an instruction tochange pressure or upon a query by the surgeon; or upon a variance ofthe pressure outside a predetermined tolerance. The surgeon's voice maybe specifically recognized so that he might state the desired pressurein an audible voice, and the machine would respond immediately that itwill seek the commanded pressure after a preset safety delay, in theabsence of further commands. Infusate selector valve 26 may also bevoice actuated. For the first time, perfusion pressure to the eye andinfusate source can be controlled directly by the surgeon rather thannecessitating the presence of other operating room personnel. Immediatepressure adjustment with voice response completes surgeon control ofinfusion pressure--the most vital parameter characterizing "closed-eye"surgery.

While we have shown out invention in two forms, it will be obvious tothose skilled in the art that it is not so limited but is susceptible ofvarious changes and modifications without departing from the spiritthereof.

What we claim is:
 1. A method of ocular perfusion using Gas ForcedLiquid Infusions (GFLI) comprising:(a) supplying pressurized gas at aselected output pressure from a gas pump; (b) pressurizing the contentsof a liquid infusate bottle with the output pressure of said gas pump;(c) supplying the contents of said liquid infusate bottle to a surgicalinfusion instrument for infusion into a selected anterior or posteriorocular chamber as an infusate; (d) selectively varying the pressure ofthe infusate within the ocular chamber by controlling the outputpressure of said gas pump; and (e) providing a human sensible indicationof the output pressure of said gas pump and providing means fordetectable audible commands;wherein said varying step comprisesdetecting audible commands to vary the pressure and adjusting the outputpressure of said gas pump in accordance with the detected audiblesignal.
 2. A method of ocular perfusion using Gas Forced Liquid Infusion(GFLI) comprising:(a) supplying pressurized gas at a selected outputpressure from a gas pump; (b) pressurizing the contents of a liquidinfusate bottle with the output pressure of said gas pump; (c) supplyingthe contents of said liquid infusate bottle to a surgical infusioninstrument for infusion into a selected anterior or posterior ocularchamber as an infusate; and (d) selectively varying the pressure of theinfusate within the ocular chamber by controlling the output pressure ofsaid gas pump; bydetecting audible commands to vary the pressure andadusting the output pressure of said gas pump in accordance with thedetected audible command signal.
 3. The method as defined in claim 2further comprising providing an audible signal acknowledging saiddetected audible command signal.
 4. A method of ocular perfusion usingGas Forced Liquid Infusion (GFLI) comprising:(a) supplying pressurizedgas at a selected output pressure from a gas pump; (b) pressurizing thecontents of a liquid infusate bottle with the output pressure of saidgas pump; (c) supplying the contents of said liquid infusate bottle to asurgical infusion instrument for infusion into a selected anterior orposterior ocular chamber as an infusate; (d) selectively varying thepressure of the infusate within the ocular chamber by controlling theoutput pressure of said gas pump; and (e) supplying gas from said gaspump to said surgical infusion instrument and selectively infusing saidocular chamber with gas or liquid infusate.
 5. A method of ocularperfusion using Gas Forced Liquid Infusion (GFLI) comprising:(a)supplying pressurized gas to a selected output pressure from a gas pump;(b) pressurizing the contents of a liquid infusate bottle with theoutput pressure of said gas pump; (c) supplying the contents of saidliquid infusate bottle to a surgical infusion instrument for infusioninto a selected anterior or posterior ocular chamber as infusate; (d)selectively varying the pressure of the infusate within the ocularchamber by controlling the output pressure of said gas pump; and (e) ahuman sensible indication of the output pressure of said gaspump;Wherein said human sensible indicator of the output pressure is aaudible signal.
 6. Apparatus for controlling the intraocular pressureduring closed wound intraocular surgery comprising:(a) a gas pump havinga variable output pressure; (b) a liquid infusate reservoir containingan infusate operatively connected to said gas pump to receivepressurized gas therefrom such that liquid infusate in said reservoir ispressurized in accordance with the output pressure of said gas pump,with said reservoir confining both said liquid infusate and a volume ofgas in direct communication with said gas pump; (c) an ocular surgicalinfusion instrument operatively connected to said liquid infusatereservoir to receive infusate therefrom; (d) means for varying thepressure of said gas pump; (e) means for providing a human sensibleindication of the output pressure of said gas pump; and (f) meansconnected to said gas pump for controlling the output pressure of saidgas pump by audible commands.
 7. Apparatus as defined in claim 6 furtherproviding means for enunciating the output pressure of said gas pumpresponsive to an audible command.
 8. Apparatus as defined in claim 7further providing means for rapidly selecting either air or liquid orgas infusate by manually or audibly controlled infusate selector valve.